1. Field of the Invention
The present invention relates to a reel driving apparatus for use in a tape recorder such as a video cassette tape recorder, a digital audio tape recorder and the like, and more particularly to a reel driving apparatus for use in a tape recorder which can drive a supply reel and a take-up reel in a different torque by means of a single idler mechanism.
2. Description of the Prior Art
Various types of the reel driving apparatuses for use in a tape recorder are well known in the art. One conventional reel driving apparatus for use in a tape recorder is illustrated in FIGS. 1 and 2. As shown in FIGS. 1 and 2, the conventional reel driving apparatus is constituted such that a power of a direct current drive motor 1 is transmitted in different paths in case of a high speed mode such as a FF/REW mode and in case of a low speed mode such as a PLAY/UNLOADING mode. That is, in the high speed mode the power of the drive motor 1 is directly transmitted to a supply reel 4 and a take-up reel 5 through upper gears 2a and 3a of supply and take-up clutches 2 and 3, while in the low speed mode the power of the drive motor 1 is transmitted to the supply and take-up reels 4 and 5 after having been reduced in its speed through the supply and take-up clutches 2 and 3 via the lower gears 2b and 3b of the supply and take-up clutches 2 and 3.
Describing in more detail such an operation, upper and lower connecting gears 7 and 7' are rotatably mounted on a central shaft 6 which is fixed between the supply clutch 2 and the take-up clutch 3, and the connecting gears 7 and 7' are in geared relations with upper and lower idler gears 8 and 8', respectively, which are meshed with the upper and lower gears 2a, 3a and 2b, 3b of the supply and take-up clutches 2 and 3, selectively, in accordance with the rotational direction of the connecting gears 7 and 7'.
Further, a pulley 10 which is provided at its upper portion with an intermediary gear 10a meshed with the lower connecting gear 7', is mounted on a drive shaft 9 and on the upper portion of the drive shaft 9, a drive gear 11 is rotatably mounted which is provided with a small gear 11a meshed with the upper connecting gear 7.
On a shaft 12, a small gear 13 is rotatably mounted which always meshes with the drive gear 11 and on the lower side of the shaft 12, a movable gear 14 is resiliently supported by a compression coil spring 15 in a manner such that it can be moved upward and downward by an up/down movement driving unit.
In a state that the movable gear 14 is moved downward, the movable gear 14 meshes with a wheel gear 17 which is provided with a capstan shaft 16 and in case of moving upwardly by the up/down movement driving unit it is separated from the wheel gear 17. On a lower surface of the wheel gear 17, a wheel pulley 18 is integrally formed which is connected with a drive pulley 19 of the drive motor 1 by means of a belt 20, and a lower pulley 21 which is fixed on the lower end of the capstan shaft 16, is connected to the driven pulley 10 by means of a belt 22.
The up/down movement driving unit comprises a swing lever 24 which is pivotable about a hinge 23 by a function plate (not shown), and an up/down member 26 for pushing upwardly the movable gear 14 by means of a pivoting motion of the swing lever 24, which is rotatably mounted on a shaft 25.
In addition, an additional latching mechanism (not shown) with a complicated structure is provided to prevent the lower idler gear 8 from being meshed with lower gears 2b and 3b of the supply and take-up clutches 2 and 3 in a high speed mode.
The conventional reel driving apparatus is operated as follows.
When a selection key is pressed for a high speed mode, the power of the drive motor 1 is transmitted in a path of drive pulley 19.fwdarw., belt 20.fwdarw., wheel pulley 18, and since at this moment the up/down movement driving unit does not operate, the movable gear 14 is moved downwardly by the restoration force of the compressed coil spring 5 and then meshed with the wheel gear 17.
Accordingly, the rotational force of the wheel gear 17 is transmitted in a path of movable gear 14.fwdarw.small gear 13.fwdarw., drive gear 11.fwdarw.upper connecting gear 7 and the upper idler gear 8 is meshed with the upper gears 2a and 3a of the supply and take-up clutches 2 and 3, selectively, in accordance with the rotational direction of the upper connecting gear 7 so that the rotational force of the upper connecting gear 7 is transmitted to the supply or take-up clutch 2 or 3, thereby rotating the supply or take-up reel 4 or 5 which is meshed with the clutches 2 and 3 in a high speed. At this time, the rotational force transmitted to the wheel pulley 21 is transmitted in a path of belt 22.fwdarw., driven pulley 10.fwdarw.intermediate gear 10a.fwdarw.lower connecting gear 7', but since the lower idler gear 8' is held by a separate latching mechanism, it rotates idle but not swung in the left or right.
On the other hand, when a selection key for low speed mode is pressed, the swing lever 24 is rotated in a counterclockwise direction about the shaft 23 by a movement of the function plate so that the up/down member 26 pushes the movable gear 14, upwardly as shown in FIG. 2, thereby separating the movable gear 14 from the wheel gear 17. Accordingly, the rotation force of the drive motor 1 is not transmitted to the movable gear 14, and the rotational force of the wheel gear 17 is transmitted in a path of wheel pulley 21, belt 20.fwdarw.driven pulley 10.fwdarw.intermediate gear 10a, lower connecting gear 7', and in accordance with the rotational direction of the lower connecting gear 7' the lower idler gear 8' meshes with lower gear 2b or 3b of the supply and take-up reels 2 and 3, selectively. At this moment, since the latching mechanism is released in the low speed mode, the movement of the lower idler gear 8' in the left and right is not restricted.
The power transmitted to the lower gears 2b and 3b of the supply and take-up clutches 2 and 3 is changed in its torque properly by means of an ordinary speed reduction operation of the clutches so that the supply and take-up reels 2 and 3 can be rotated with a rotational force suitable for a low speed mode.
However, in such a conventional reel driving apparatus, since two pairs of idler mechanisms having different power transmitting paths are used to drive the supply and take-up reels in a torque suitable for a high speed mode and a low speed mode, respectively, there is a disadvantage in that the structure becomes complicated on the whole, resulting in the high cost and low productivity.